Systems and methods for signaling picture order count values for pictures included in coded video

ABSTRACT

Some embodiments include a method of signaling picture count information for decoding video pictures. The method sends a picture order count (POC) most significant bit (MSB) first flag indicating that a picture order count most significant bit second flag is present. The method sends the POC MSB second flag to indicate whether a POC MSB cycle element is present. When a value of the POC MSB present flag is true, the method sends the POC MSB element specifying a value of a POC MSB cycle.

CROSS REFERENCE

This Nonprovisional application claims priority under 35 U.S.C. § 119 onprovisional Application No. 62/692,839 on Jul. 1, 2018, No. 62/739,059on Sep. 28, 2018, No. 62/752,226 on Oct. 29, 2018, the entire contentsof which are hereby incorporated by reference.

CLAIM OF BENEFIT TO PRIOR APPLICATIONS

This application is a national stage application of International PatentApplication PCT/JP2019/025981, filed Jun. 28, 2019, now published asWO2020/009044. International Patent Application PCT/JP2019/025981 claimsthe benefit of U.S. Provisional Patent Applications 62/692,839, filedJul. 1, 2018; 62/739,059, filed Sep. 28, 2018; and 62/752,226, filedOct. 29, 2018. U.S. Provisional Patent Applications 62/692,839,62/739,059, and 62/752,226, and International Patent ApplicationPCT/JP2019/025981, now published as WO2020/009044, are incorporatedherein by reference.

TECHNICAL FIELD

This disclosure relates to video coding and more particularly totechniques for signaling of pictures order count values in coded video.

BACKGROUND ART

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, laptop or desktop computers,tablet computers, digital recording devices, digital media players,video gaming devices, cellular telephones, including so-calledsmartphones, medical imaging devices, and the like. Digital video may becoded according to a video coding standard. Video coding standards mayincorporate video compression techniques. Examples of video codingstandards include ISO/IEC MPEG4 Visual and ITU-T H.264 (also known asISO/IEC MPEG-4 AVC) and High-Efficiency Video Coding (HEVC). HEVC isdescribed in High Efficiency Video Coding (HEVC), Rec. ITU-T H.265,December 2016, which is incorporated by reference, and referred toherein as ITU-T H.265. Extensions and improvements for ITU-T H.265 arecurrently being considered for the development of next generation videocoding standards. For example, the ITU-T Video Coding Experts Group(VCEG) and ISO/IEC (Moving Picture Experts Group (MPEG) (collectivelyreferred to as the Joint Video Exploration Team (JVET)) are studying thepotential need for standardization of future video coding technologywith a compression capability that significantly exceeds that of thecurrent HEVC standard. The Joint Exploration Model 7 (JEM 7), AlgorithmDescription of Joint Exploration Test Model 7 (JEM 7), ISO/IECJTC1/SC29/WG11 Document: JVET-G1001, July 2017, Torino, IT, which isincorporated by reference herein, describes the coding features undercoordinated test model study by the JVET as potentially enhancing videocoding technology beyond the capabilities of ITU-T H.265. It should benoted that the coding features of JEM 7 are implemented in JEM referencesoftware. As used herein, the term JEM may collectively refer toalgorithms included in JEM 7 and implementations of JEM referencesoftware. Further, in response to a “Joint Call for Proposals on VideoCompression with Capabilities beyond HEVC,” jointly issued by VCEG andMPEG, multiple descriptions of video coding were proposed by variousgroups at the 10^(th) Meeting of ISO/IEC JTC1/SC29/WG11 16-20 Apr. 2018,San Diego, Calif. As a result of the multiple descriptions of videocoding, a draft text of a video coding specification is described in“Versatile Video Coding (Draft 1),” 10^(th) Meeting of ISO/IECJTC1/SC29/WG11 16-20 Apr. 2018, San Diego, Calif., documentJVET-J1001-v2, which is incorporated by reference herein, and referredto as JVET-J1001.

Video compression techniques reduce data requirements for storing andtransmitting video data by exploiting the inherent redundancies in avideo sequence. Video compression techniques may sub-divide a videosequence into successively smaller portions (i.e., groups of frameswithin a video sequence, a frame within a group of frames, slices withina frame, coding tree units (e.g., macroblocks) within a slice, codingblocks within a coding tree unit, etc.). Intra prediction codingtechniques (e.g., intra-picture (spatial)) and inter predictiontechniques (i.e., inter-picture (temporal)) may be used to generatedifference values between a unit of video data to be coded and areference unit of video data. The difference values may be referred toas residual data. Residual data may be coded as quantized transformcoefficients. Syntax elements may relate residual data and a referencecoding unit (e.g., intra-prediction mode indices, motion vectors, andblock vectors). Residual data and syntax elements may be entropy coded.Entropy encoded residual data and syntax elements may be included in acompliant bitstream. Compliant bitstreams and associated metadata may beformatted according to data structures.

SUMMARY OF INVENTION

In one example, a method of signaling picture count information, themethod including:

sending a picture order count most significant bit present flagindicating whether a picture order count most significant bit cycleelement is present; and sending the picture order count most significantbit cycle element specifying a value of a picture order count mostsignificant bit cycle if a value of the picture order count mostsignificant bit present flag is equal to one, wherein a maximum value ofthe picture order count most significant bit cycle element is set byusing a maximum picture order count least significant bit minus fourelement.

In one example, a method of decoding video data, the method including:decoding a picture order count most significant bit present flagindicating whether a picture order count most significant bit cycleelement is present; and decoding the picture order count mostsignificant bit cycle element specifying a value of a picture ordercount most significant bit cycle if a value of the picture order countmost significant bit present flag is equal to one, wherein a maximumvalue of the picture order count most significant bit cycle element isset by using a maximum picture order count least significant bit minusfour element.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example of a system that maybe configured to encode and decode video data according to one or moretechniques of this this disclosure.

FIG. 2 is a conceptual diagram illustrating coded video data andcorresponding data structures according to one or more techniques ofthis this disclosure.

FIG. 3 is a conceptual diagram illustrating a data structureencapsulating coded video data and corresponding metadata according toone or more techniques of this this disclosure.

FIG. 4 is a conceptual drawing illustrating an example of componentsthat may be included in an implementation of a system that may beconfigured to encode and decode video data according to one or moretechniques of this this disclosure.

FIG. 5 is a block diagram illustrating an example of a video encoderthat may be configured to encode video data according to one or moretechniques of this disclosure.

FIG. 6 is a block diagram illustrating an example of a video decoderthat may be configured to decode video data according to one or moretechniques of this disclosure.

DESCRIPTION OF EMBODIMENTS

In general, this disclosure describes various techniques for codingvideo data. In particular, this disclosure describes techniques forsignaling of picture types of coded video. Signaling of picture typesaccording to the techniques described herein may be particularly usefulfor improving video distribution system performance by loweringtransmission bandwidth and/or facilitating parallelization of a videoencoder and/or decoder. It should be noted that although techniques ofthis disclosure are described with respect to ITU-T H.264, ITU-T H.265,and JVET-J1001 the techniques of this disclosure are generallyapplicable to video coding. For example, the coding techniques describedherein may be incorporated into video coding systems, (including videocoding systems based on future video coding standards) including blockstructures, intra prediction techniques, inter prediction techniques,transform techniques, filtering techniques, and/or entropy codingtechniques other than those included in ITU-T H.265. Thus, reference toITU-T H.264, ITU-T H.265, and JVET-J1001 is for descriptive purposes andshould not be construed to limit the scope of the techniques describedherein. Further, it should be noted that incorporation by reference ofdocuments herein should not be construed to limit or create ambiguitywith respect to terms used herein. For example, in the case where anincorporated reference provides a different definition of a term thananother incorporated reference and/or as the term is used herein, theterm should be interpreted in a manner that broadly includes eachrespective definition and/or in a manner that includes each of theparticular definitions in the alternative.

In one example, a method of signaling picture count information includesdetermining a picture order count most significant bit cycle value,signaling a flag in a parameter set indicating the presence of syntax ina slice header indicating a picture order count most significant bitcycle value, and signaling values for syntax elements in a slice headerindicating a picture order count most significant bit cycle value.

In one example, a device comprises one or more processors configured todetermine a picture order count most significant bit cycle value, signala flag in a parameter set indicating the presence of syntax in a sliceheader indicating a picture order count most significant bit cyclevalue, and signal values for syntax elements in a slice headerindicating a picture order count most significant bit cycle value.

In one example, a non-transitory computer-readable storage mediumcomprises instructions stored thereon that, when executed, cause one ormore processors of a device to determine a picture order count mostsignificant bit cycle value, signal a flag in a parameter set indicatingthe presence of syntax in a slice header indicating a picture ordercount most significant bit cycle value, and signal values for syntaxelements in a slice header indicating a picture order count mostsignificant bit cycle value.

In one example, an apparatus comprises means for determining a pictureorder count most significant bit cycle value, means for signaling a flagin a parameter set indicating the presence of syntax in a slice headerindicating a picture order count most significant bit cycle value, andmeans for signaling values for syntax elements in a slice headerindicating a picture order count most significant bit cycle value.

In one example, a method of decoding video data comprises parsing a flagin a parameter set indicating the presence of syntax in a slice headerindicating a picture order count most significant bit cycle value,conditionally parsing values for syntax elements in a slice headerindicating a picture order count most significant bit cycle value basedon the value of the flag in the parameter set and determining a pictureorder count most significant bit cycle value.

In one example, a device comprises one or more processors configured toparse a flag in a parameter set indicating the presence of syntax in aslice header indicating a picture order count most significant bit cyclevalue, conditionally parse values for syntax elements in a slice headerindicating a picture order count most significant bit cycle value basedon the value of the flag in the parameter set and determine a pictureorder count most significant bit cycle value.

In one example, a non-transitory computer-readable storage mediumcomprises instructions stored thereon that, when executed, cause one ormore processors of a device to parse a flag in a parameter setindicating the presence of syntax in a slice header indicating a pictureorder count most significant bit cycle value, conditionally parse valuesfor syntax elements in a slice header indicating a picture order countmost significant bit cycle value based on the value of the flag in theparameter set and determine a picture order count most significant bitcycle value.

In one example, an apparatus comprises means for parsing a flag in aparameter set indicating the presence of syntax in a slice headerindicating a picture order count most significant bit cycle value, meansfor conditionally parsing values for syntax elements in a slice headerindicating a picture order count most significant bit cycle value basedon the value of the flag in the parameter set and means for determininga picture order count most significant bit cycle value.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

Video content typically includes video sequences comprised of a seriesof frames. A series of frames may also be referred to as a group ofpictures (GOP). Each video frame or picture may include a one or moreslices, where a slice includes a plurality of video blocks. A videoblock includes an array of pixel values (also referred to as samples)that may be predictively coded. Video blocks may be ordered according toa scan pattern (e.g., a raster scan). A video encoder performspredictive encoding on video blocks and sub-divisions thereof. ITU-TH.264 specifies a macroblock including 16×16 luma samples. ITU-T H.265specifies an analogous Coding Tree Unit (CTU) structure (which may bereferred to as a Largest Coding Unit (LCU)) where a picture may be splitinto CTUs of equal size and each CTU may include Coding Tree Blocks(CTB) having 16×16, 32×32, or 64×64 luma samples. As used herein, theterm video block may generally refer to an area of a picture or may morespecifically refer to the largest array of pixel values that may bepredictively coded, sub-divisions thereof, and/or correspondingstructures. Further, according to ITU-T H.265, each video frame orpicture may be partitioned to include one or more tiles, where a tile isa sequence of coding tree units corresponding to a rectangular area of apicture.

In ITU-T H.265, a CTU is composed of respective CTBs for each componentof video data (e.g., luma (Y) and chroma (Cb and Cr)). Further, in ITU-TH.265, a CTU may be partitioned according to a quadtree (QT)partitioning structure, which results in the CTBs of the CTU beingpartitioned into Coding Blocks (CB). That is, in ITU-T H.265, a CTU maybe partitioned into quadtree leaf nodes. According to ITU-T H.265, oneluma CB together with two corresponding chroma CBs and associated syntaxelements are referred to as a coding unit (CU). In ITU-T H.265, aminimum allowed size of a CB may be signaled. In ITU-T H.265, thesmallest minimum allowed size of a luma CB is 8×8 luma samples. In ITU-TH.265, the decision to code a picture area using intra prediction orinter prediction is made at the CU level.

In ITU-T H.265, a CU is associated with a prediction unit (PU) structurehaving its root at the CU. In ITU-T H.265, PU structures allow luma andchroma CBs to be split for purposes of generating correspondingreference samples. That is, in ITU-T H.265, luma and chroma CBs may besplit into respect luma and chroma prediction blocks (PBs), where a PBincludes a block of sample values for which the same prediction isapplied. In ITU-T H.265, a CB may be partitioned into 1, 2, or 4 PBs.ITU-T H.265 supports PB sizes from 64×64 samples down to 4×4 samples. InITU-T H.265, square PBs are supported for intra prediction, where a CBmay form the PB or the CB may be split into four square PBs (i.e., intraprediction PB sizes type include M×M or M/2×M/2, where M is the heightand width of the square CB). In ITU-T H.265, in addition to the squarePBs, rectangular PBs are supported for inter prediction, where a CB mayby halved vertically or horizontally to form PBs (i.e., inter predictionPB types include M×M, M/2×M/2, M/2×M, or M×M/2). Further, it should benoted that in ITU-T H.265, for inter prediction, four asymmetric PBpartitions are supported, where the CB is partitioned into two PBs atone quarter of the height (at the top or the bottom) or width (at theleft or the right) of the CB (i.e., asymmetric partitions include M/4×Mleft, M/4×M right, M×M/4 top, and M×M/4 bottom). Intra prediction data(e.g., intra prediction mode syntax elements) or inter prediction data(e.g., motion data syntax elements) corresponding to a PB is used toproduce reference and/or predicted sample values for the PB.

JEM specifies a CTU having a maximum size of 256×256 luma samples. JEMspecifies a quadtree plus binary tree (QTBT) block structure. In JEM,the QTBT structure enables quadtree leaf nodes to be further partitionedby a binary tree (BT) structure. That is, in JEM, the binary treestructure enables quadtree leaf nodes to be recursively dividedvertically or horizontally. Thus, the binary tree structure in JEMenables square and rectangular leaf nodes, where each leaf node includesa CB. As illustrated in FIG. 2, a picture included in a GOP may includeslices, where each slice includes a sequence of CTUs and each CTU may bepartitioned according to a QTBT structure. In JEM, CBs are used forprediction without any further partitioning. That is, in JEM, a CB maybe a block of sample values on which the same prediction is applied.Thus, a JEM QTBT leaf node may be analogous a PB in ITU-T H.265.

Intra prediction data (e.g., intra prediction mode syntax elements) orinter prediction data (e.g., motion data syntax elements) may associatePUs with corresponding reference samples. Residual data may includerespective arrays of difference values corresponding to each componentof video data (e.g., luma (Y) and chroma (Cb and Cr)). Residual data maybe in the pixel domain. A transform, such as, a discrete cosinetransform (DCT), a discrete sine transform (DST), an integer transform,a wavelet transform, or a conceptually similar transform, may be appliedto pixel difference values to generate transform coefficients. It shouldbe noted that in ITU-T H.265, CUs may be further sub-divided intoTransform Units (TUs). That is, an array of pixel difference values maybe sub-divided for purposes of generating transform coefficients (e.g.,four 8×8 transforms may be applied to a 16×16 array of residual valuescorresponding to a 16×16 luma CB), such sub-divisions may be referred toas Transform Blocks (TBs). Transform coefficients may be quantizedaccording to a quantization parameter (QP). Quantized transformcoefficients (which may be referred to as level values) may be entropycoded according to an entropy encoding technique (e.g., content adaptivevariable length coding (CAVLC), context adaptive binary arithmeticcoding (CABAC), probability interval partitioning entropy coding (PIPE),etc.). Further, syntax elements, such as, a syntax element indicating aprediction mode, may also be entropy coded. Entropy encoded quantizedtransform coefficients and corresponding entropy encoded syntax elementsmay form a compliant bitstream that can be used to reproduce video data.A binarization process may be performed on syntax elements as part of anentropy coding process. Binarization refers to the process of convertinga syntax value into a series of one or more bits. These bits may bereferred to as “bins.”

As described above, intra prediction data or inter prediction data isused to produce reference sample values for a block of sample values.The difference between sample values included in a current PB, oranother type of picture area structure, and associated reference samples(e.g., those generated using a prediction) may be referred to asresidual data. As described above, intra prediction data or interprediction data may associate an area of a picture (e.g., a PB or a CB)with corresponding reference samples. For intra prediction coding, anintra prediction mode may specify the location of reference sampleswithin a picture. In ITU-T H.265, defined possible intra predictionmodes include a planar (i.e., surface fitting) prediction mode(predMode: 0), a DC (i.e., flat overall averaging) prediction mode(predMode: 1), and 33 angular prediction modes (predMode: 2-34). In JEM,defined possible intra-prediction modes include a planar prediction mode(predMode: 0), a DC prediction mode (predMode: 1), and 65 angularprediction modes (predMode: 2-66). It should be noted that planar and DCprediction modes may be referred to as non-directional prediction modesand that angular prediction modes may be referred to as directionalprediction modes. It should be noted that the techniques describedherein may be generally applicable regardless of the number of definedpossible prediction modes.

For inter prediction coding, a motion vector (MV) identifies referencesamples in a picture other than the picture of a video block to be codedand thereby exploits temporal redundancy in video. For example, acurrent video block may be predicted from reference block(s) located inpreviously coded frame(s) and a motion vector may be used to indicatethe location of the reference block. A motion vector and associated datamay describe, for example, a horizontal component of the motion vector,a vertical component of the motion vector, a resolution for the motionvector (e.g., one-quarter pixel precision, one-half pixel precision,one-pixel precision, two-pixel precision, four-pixel precision), aprediction direction and/or a reference picture index value. Further, acoding standard, such as, for example ITU-T H.265, may support motionvector prediction. Motion vector prediction enables a motion vector tobe specified using motion vectors of neighboring blocks. Examples ofmotion vector prediction include advanced motion vector prediction(AMVP), temporal motion vector prediction (TMVP), so-called “merge”mode, and “skip” and “direct” motion inference. Further, JEM supportsadvanced temporal motion vector prediction (ATMVP), Spatial-temporalmotion vector prediction (STMVP), Pattern matched motion vectorderivation (PMMVD) mode, which is a special merge mode based onFrame-Rate Up Conversion (FRUC) techniques, and affine transform motioncompensation prediction.

Residual data may include respective arrays of difference valuescorresponding to each component of video data. Residual data may be inthe pixel domain. A transform, such as, a discrete cosine transform(DCT), a discrete sine transform (DST), an integer transform, a wavelettransform, or a conceptually similar transform, may be applied to anarray of difference values to generate transform coefficients. In ITU-TH.265, a CU is associated with a transform unit (TU) structure havingits root at the CU level. That is, in ITU-T H.265, as described above,an array of difference values may be sub-divided for purposes ofgenerating transform coefficients (e.g., four 8×8 transforms may beapplied to a 16×16 array of residual values). It should be noted that inITU-T H.265, TBs are not necessarily aligned with PBs.

It should be noted that in JEM, residual values corresponding to a CBare used to generate transform coefficients without furtherpartitioning. That is, in JEM a QTBT leaf node may be analogous to botha PB and a TB in ITU-T H.265. It should be noted that in JEM, a coretransform and a subsequent secondary transforms may be applied (in thevideo encoder) to generate transform coefficients. For a video decoder,the order of transforms is reversed. Further, in JEM, whether asecondary transform is applied to generate transform coefficients may bedependent on a prediction mode.

A quantization process may be performed on transform coefficients.Quantization approximates transform coefficients by amplitudesrestricted to a set of specified values. Quantization may be used inorder to vary the amount of data required to represent a group oftransform coefficients. Quantization may be realized through division oftransform coefficients by a scaling factor and any associated roundingfunctions (e.g., rounding to the nearest integer). Quantized transformcoefficients may be referred to as coefficient level values. Inversequantization (or “dequantization”) may include multiplication ofcoefficient level values by the scaling factor. It should be noted thatas used herein the term quantization process in some instances may referto division by a scaling factor to generate level values ormultiplication by a scaling factor to recover transform coefficients insome instances. That is, a quantization process may refer toquantization in some cases and inverse quantization in some cases.

With respect to the equations used herein, the following arithmeticoperators may be used:

-   -   + Addition    -   − Subtraction    -   * Multiplication, including matrix multiplication    -   x^(y) Exponentiation. Specifies x to the power of y. In other        contexts, such notation is used for superscripting not intended        for interpretation as exponentiation.    -   / Integer division with truncation of the result toward zero.        For example, 7/4 and −7/−4 are truncated to 1 and −7/4 and 7/−4        are truncated to −1.    -   ÷ Used to denote division in mathematical equations where no        truncation or rounding is intended.

$\frac{x}{y}$Used to denote division in mathematical equations where no truncation orrounding is intended.

Further, the following mathematical functions may be used:

-   -   Log 2(x) the base-2 logarithm of x;

${{Min}( {x,y} )} = \{ {\begin{matrix}{x;} & {x<=y} \\{y;} & {x > y}\end{matrix};{{{Max}( {x,y} )} = \{ \begin{matrix}{x;} & {x>=y} \\{y;} & {x < y}\end{matrix} }} $

-   -   Ceil(x) the smallest integer greater than or equal to x.

With respect to the example syntax used herein, the followingdefinitions of logical operators may be applied:

-   -   x && y Boolean logical “and” of x and y    -   x∥y Boolean logical “or” of x and y    -   ! Boolean logical “not”    -   x? y:z If x is TRUE or not equal to 0, evaluates to the value of        y; otherwise, evaluates to the value of z.

Further, the following relational operators may be applied:

-   -   > Greater than    -   >= Greater than or equal to    -   < Less than    -   <= Less than or equal to    -   == Equal to    -   != Not equal to

Further, it should be noted that in the syntax descriptors used herein,the following descriptors may be applied:

-   -   f(n): fixed-pattern bit string using n bits written (from left        to right) with the left bit first. The parsing process for this        descriptor is specified by the return value of the function        read_bits(n).    -   u(n): unsigned integer using n bits. When n is “v” in a syntax        table, the number of bits varies in a manner dependent on the        value of other syntax elements. The parsing process for this        descriptor is specified by the return value of the function        read_bits(n) interpreted as a binary representation of an        unsigned integer with most significant bit written first.    -   ue(v): unsigned integer 0-th order Exp-Golomb-coded syntax        element with the left bit first.    -   i(n): signed integer using n bits. When n is “v” in a syntax        table, the number of bits varies in a manner dependent on the        value of other syntax elements. The parsing process for this        descriptor is specified by the return value of the function        read_bits(n) interpreted as a two's complement integer        representation with most significant bit written first.

As described above, according to ITU-T H.265, each video frame orpicture may be partitioned to include one or more slices and furtherpartitioned to include one or more tiles. FIG. 2 is a conceptual diagramillustrating an example of a group of pictures including slices. In theexample illustrated in FIG. 2, Pic₄ is illustrated as including twoslices (i.e., Slice₁ and Slice₂) where each slice includes a sequence ofCTUs (e.g., in raster scan order). It should be noted that a slice is asequence of one or more slice segments starting with an independentslice segment and containing all subsequent dependent slice segments (ifany) that precede the next independent slice segment (if any) within thesame access unit. A slice segment, like a slice, is a sequence of codingtree units. In the examples described herein, in some cases the termsslice and slice segment may be used interchangeably to indicate asequence of coding tree units. It should be noted that in ITU-T H.265, atile may consist of coding tree units contained in more than one sliceand a slice may consist of coding tree units contained in more than onetile. However, ITU-T H.265 provides that one or both of the followingconditions shall be fulfilled: (1) All coding tree units in a slicebelong to the same tile; and (2) All coding tree units in a tile belongto the same slice. Tile sets may be used to define boundaries for codingdependencies (e.g., intra-prediction dependencies, entropy encodingdependencies, etc.) and as such, may enable parallelism in coding.

In ITU-T H.265, a coded video sequence (CVS) may be encapsulated (orstructured) as a sequence of access units, where each access unitincludes video data structured as network abstraction layer (NAL) units.In ITU-T H.265, a bitstream is described as including a sequence of NALunits forming one or more CVSs. It should be noted that ITU-T H.265supports multi-layer extensions, including format range extensions(RExt), scalability (SHVC), multi-view (MV-HEVC), and 3-D (3D-HEVC).Multi-layer extensions enable a video presentation to include a baselayer and one or more additional enhancement layers. For example, a baselayer may enable a video presentation having a basic level of quality(e.g., High Definition rendering) to be presented and an enhancementlayer may enable a video presentation having an enhanced level ofquality (e.g., an Ultra High Definition rendering) to be presented. InITU-T H.265, an enhancement layer may be coded by referencing a baselayer. That is, for example, a picture in an enhancement layer may becoded (e.g., using inter prediction techniques) by referencing one ormore pictures (including scaled versions thereof) in a base layer. InITU-T H.265, each NAL unit may include an identifier indicating a layerof video data the NAL unit is associated with. It should be noted thatsub-bitstream extraction may refer to a process where a device receivinga compliant bitstream forms a new compliant bitstream by discardingand/or modifying data in the received bitstream. For example,sub-bitstream extraction may be used to form a new compliant bitstreamcorresponding to a particular representation of video (e.g., a highquality representation).

Referring to the example illustrated in FIG. 2, each slice of video dataincluded in Pic₄ (i.e., Slice₁ and Slice₂) is illustrated as beingencapsulated in a NAL unit. In ITU-T H.265, each of a video sequence, aGOP, a picture, a slice, and CTU may be associated with metadata thatdescribes video coding properties. ITU-T H.265 defines parameters setsthat may be used to describe video data and/or video coding properties.In ITU-T H.265, parameter sets may be encapsulated as a special type ofNAL unit or may be signaled as a message. NAL units including codedvideo data (e.g., a slice) may be referred to as VCL (Video CodingLayer) NAL units and NAL units including metadata (e.g., parameter sets)may be referred to as non-VCL NAL units. Further, ITU-T H.265 enablessupplemental enhancement information (SEI) messages to be signaled. InITU-T H.265, SEI messages assist in processes related to decoding,display or other purposes, however, SEI messages may not be required forconstructing the luma or chroma samples by the decoding process. InITU-T H.265, SEI messages may be signaled in a bitstream using non-VCLNAL units. Further, SEI messages may be conveyed by some means otherthan by being present in the bitstream (i.e., signaled out-of-band).

FIG. 3 illustrates an example of a bitstream including multiple CVSs,where a CVS is represented by NAL units included in a respective accessunit. In the example illustrated in FIG. 3, non-VCL NAL units includerespective parameter set units (i.e., Video Parameter Sets (VPS),Sequence Parameter Sets (SPS), and Picture Parameter Set (PPS) units)and an access unit delimiter NAL unit. ITU-T H.265 defines NAL unitheader semantics that specify the type of Raw Byte Sequence Payload(RBSP) data structure included in the NAL unit. It should be noted thatITU-T H.265 provides various picture types which are defined based ondecoding order and/or output order. In ITU-T H.265, an intra randomaccess point (TRAP) picture is a picture that does not refer to anypictures other than itself for inter prediction in its decoding processand the first picture in the bitstream in decoding order must be an IRAPpicture. It should be noted in ITU-T H.265 that there may be pictures ina bitstream that do not refer to any pictures other than itself forinter prediction in its decoding process that are not IRAP pictures. Anexample of an IRAP pictures includes an instantaneous decoding refresh(IDR) picture which is a picture that does not refer to any picturesother than itself for inter prediction in its decoding process, and maybe the first picture in the bitstream in decoding order, or may appearlater in the bitstream. ITU-T H.265 provides where a leading picture isa picture that precedes the associated IRAP picture in output order anda trailing picture is a non-IRAP picture that follows the associatedIRAP picture in output order. It should be noted that trailing picturesassociated with an IRAP picture also follow the IRAP picture in decodingorder and pictures that follow the associated IRAP picture in outputorder and precede the associated IRAP picture in decoding order are notallowed.

ITU-T H.265 provides where each coded picture is associated with apicture order count variable, denoted as PicOrderCntVal. In ITU-T H.265,picture order counts are used to identify pictures, for deriving motionparameters in merge mode and motion vector prediction, and for decoderconformance checking. In ITU-T H.265, in one CVS, the PicOrderCntValvalues for all coded pictures is unique. Further, in ITU-T H.265 pictureorder counts provide the relative output order of pictures (i.e., from adecoded picture buffer, e.g., for display) included in a CVS (i.e.,pictures with lower picture order counts are output before pictures witha higher picture order counts). In ITU-T H.265, the value ofPicOrderCntVal is in the range of −2³¹ to 2³¹⁻¹, inclusive. In ITU-TH.265, the sequence parameter set syntax includes syntax element log2_max_pic_order_cnt_lsb_minus4 which specifies the value of a variableMaxPicOrderCntLsb that is used in the decoding process for picture ordercount as follows:MaxPicOrderCntLsb=2^((log2_max_pic_order_cnt_lsb_minus4+4))

-   -   Where the value of log 2_max_pic_order_cnt_lsb_minus4 shall be        in the range of 0 to 12, inclusive.        ITU-T H.265 provides where a PicOrderCntVal is equal to        PicOrderCntMsb+slice_pic_order_cnt_lsb. slice_pic_order_cnt_lsb        is derived as follows:    -   When the current picture is not an IRAP picture and output, the        variable prevPicOrderCntLsb is derived as follows:        -   Let prevTid0Pic be the previous picture in decoding order            that has TemporalId equal to 0 and that is not a random            access skipped leading (RASL), a random access decodable            leading (RADL), or a sub-layer non-reference (SLNR) picture.        -   The variable prevPicOrderCntLsb is set equal to the            slice_pic_order_cnt_lsb of prevTid0Pic.    -   Where the syntax element slice_pic_order_cnt_lsb is        conditionally included in the slice_segment_header( ) syntax        when a picture is not an IRAP picture and the has the following        definition:    -   slice_pic_order_cnt_lsb specifies the picture order count modulo        MaxPicOrderCntLsb for the current picture. The length of the        slice_pic_order_cnt_lsb syntax element is log        2_max_pic_order_cnt_lsb_minus4+4 bits. The value of the        slice_pic_order_cnt_lsb shall be in the range of 0 to        MaxPicOrderCntLsb−1, inclusive. When slice_pic_order_cnt_lsb is        not present, slice_pic_order_cnt_lsb is inferred to be equal to        0 (for cases other than a generated picture).

In ITU-T H.265 PicOrderCntMsb is derived as follows:

-   -   When the current picture is not an IRAP picture and output, the        variable prevPicOrderCntLsb is derived as follows:        -   The variable prevPicOrderCntMsb is set equal to            PicOrderCntMsb of prevTid0Pic.        -   If the current picture is an IRAP picture with            NoRaslOutputFlag equal to 1, PicOrderCntMsb is set equal to            0.        -   Otherwise, PicOrderCntMsb is derived as follows:    -   if((slice_pic_order_cnt_lsb<prevPicOrderCntLsb) &&        ((prevPicOrderCntLsb−slice_pic_order_cnt_lsb)>=(MaxPicOrderCntLsb/2)))        -   PicOrderCntMsb=prevPicOrderCntMsb+MaxPicOrderCntLsb    -   else if((slice_pic_order_cnt_lsb>prevPicOrderCntLsb) &&        ((slice_pic_order_cnt_lsb−prevPicOrderCntLsb)>(MaxPicOrderCntLsb/2)))        -   PicOrderCntMsb=prevPicOrderCntMsb−MaxPicOrderCntLsb    -   else    -   PicOrderCntMsb=prevPicOrderCntMsb

It should be noted that in ITU-T H.265, all IDR pictures will havePicOrderCntVal equal to 0 since slice_pic_order_cnt_lsb is inferred tobe 0 for IDR pictures and prevPicOrderCntLsb and prevPicOrderCntMsb areboth set equal to 0.

It should be noted that JVET-J1001 provides the slice head syntaxillustrated in Table 1.

TABLE 1 Descriptor slice_header( ) {  slice_pic_parameter_set_id ue(v) slice_address u(v)  slice_type ue(v)  if ( slice_type != I )  log2_diff_ctu_max_bt_size ue(v)  byte_alignment( ) }

JVET-J1001 provides the following definitions for the respective syntaxelements illustrated in Table 1.

-   -   slice_pic_parameter_set_id specifies the value of        pps_pic_parameter_set_id for the PPS in use. The value of        slice_pic_parameter_set_id shall be in the range of 0 to 63,        inclusive.    -   slice_address specifies the address of the first CTB in the        slice, in CTB raster scan of a picture. The length of the        slice_address syntax element is Ceil(Log 2(PicSizeInCtbsY))        bits. The value of slice_address shall be in the range of 0 to        PicSizeInCtbsY−1, inclusive, and the value of slice_address        shall not be equal to the value of slice_address of any other        coded slice NAL unit of the same coded picture.    -   The variable CtbAddrInRs, specifying a CTB address in CTB raster        scan of a picture, is set equal to slice_address.    -   slice_type specifies the coding type of the slice according to        Table 2.

TABLE 2 slice_type Name of slice_type 0 B (B slice) 1 P (P slice) 2 I (Islice)

-   -   When nal_unit_type has a value in the range of [to be        determined], inclusive, i.e., the picture is an IRAP picture,        slice_type shall be equal to 2.    -   log 2_diff_ctu_max_bt_size specifies the difference between the        luma CTB size and the maximum luma size (width or height) of a        coding block that can be split using a binary split. The value        of log 2_diff_ctu_max_bt_size shall be in the range of 0 to        CtbLog2SizeY−MinCbLog2SizeY, inclusive.

It should be noted that a B slice refers to a slice where bi-predictioninter prediction, uni-prediction inter prediction, and intra predicationare allowed; a P slice refers to a slice where uni-prediction interprediction, and intra predication are allowed; and a I slice referswhere only intra predication is allowed. It should be noted that in somecases B and P slices are collectively referred to as inter slices

This disclosure describes techniques for signaling picture order countvalues, which are simplified and provide more flexibility compared tothrough described in ITU-T H.265. According to the techniques describedherein, a video encoder may signal picture order count values and thelike using the syntax and semantics described herein. A video decodermay determine picture order count values and the like by parsingsignaling that uses the syntax and semantics described herein andperform video decoding and output pictures based on the determinedpicture order count values.

FIG. 1 is a block diagram illustrating an example of a system that maybe configured to code (i.e., encode and/or decode) video data accordingto one or more techniques of this disclosure. System 100 represents anexample of a system that may encapsulate video data according to one ormore techniques of this disclosure. As illustrated in FIG. 1, system 100includes source device 102, communications medium 110, and destinationdevice 120. In the example illustrated in FIG. 1, source device 102 mayinclude any device configured to encode video data and transmit encodedvideo data to communications medium 110. Destination device 120 mayinclude any device configured to receive encoded video data viacommunications medium 110 and to decode encoded video data. Sourcedevice 102 and/or destination device 120 may include computing devicesequipped for wired and/or wireless communications and may include, forexample, set top boxes, digital video recorders, televisions, desktop,laptop or tablet computers, gaming consoles, medical imagining devices,and mobile devices, including, for example, smartphones, cellulartelephones, personal gaming devices.

Communications medium 110 may include any combination of wireless andwired communication media, and/or storage devices. Communications medium110 may include coaxial cables, fiber optic cables, twisted pair cables,wireless transmitters and receivers, routers, switches, repeaters, basestations, or any other equipment that may be useful to facilitatecommunications between various devices and sites. Communications medium110 may include one or more networks. For example, communications medium110 may include a network configured to enable access to the World WideWeb, for example, the Internet. A network may operate according to acombination of one or more telecommunication protocols.Telecommunications protocols may include proprietary aspects and/or mayinclude standardized telecommunication protocols. Examples ofstandardized telecommunications protocols include Digital VideoBroadcasting (DVB) standards, Advanced Television Systems Committee(ATSC) standards, Integrated Services Digital Broadcasting (ISDB)standards, Data Over Cable Service Interface Specification (DOCSIS)standards, Global System Mobile Communications (GSM) standards, codedivision multiple access (CDMA) standards, 3rd Generation PartnershipProject (3GPP) standards, European Telecommunications StandardsInstitute (ETSI) standards, Internet Protocol (IP) standards, WirelessApplication Protocol (WAP) standards, and Institute of Electrical andElectronics Engineers (IEEE) standards.

Storage devices may include any type of device or storage medium capableof storing data. A storage medium may include a tangible ornon-transitory computer-readable media. A computer readable medium mayinclude optical discs, flash memory, magnetic memory, or any othersuitable digital storage media. In some examples, a memory device orportions thereof may be described as non-volatile memory and in otherexamples portions of memory devices may be described as volatile memory.Examples of volatile memories may include random access memories (RAM),dynamic random access memories (DRAM), and static random access memories(SRAM). Examples of non-volatile memories may include magnetic harddiscs, optical discs, floppy discs, flash memories, or forms ofelectrically programmable memories (EPROM) or electrically erasable andprogrammable (EEPROM) memories. Storage device(s) may include memorycards (e.g., a Secure Digital (SD) memory card), internal/external harddisk drives, and/or internal/external solid state drives. Data may bestored on a storage device according to a defined file format.

FIG. 4 is a conceptual drawing illustrating an example of componentsthat may be included in an implementation of system 100. In the exampleimplementation illustrated in FIG. 4, system 100 includes one or morecomputing devices 402A-402N, television service network 404, televisionservice provider site 406, wide area network 408, local area network410, and one or more content provider sites 412A-412N. Theimplementation illustrated in FIG. 4 represents an example of a systemthat may be configured to allow digital media content, such as, forexample, a movie, a live sporting event, etc., and data and applicationsand media presentations associated therewith to be distributed to andaccessed by a plurality of computing devices, such as computing devices402A-402N. In the example illustrated in FIG. 4, computing devices402A-402N may include any device configured to receive data from one ormore of television service network 404, wide area network 408, and/orlocal area network 410. For example, computing devices 402A-402N may beequipped for wired and/or wireless communications and may be configuredto receive services through one or more data channels and may includetelevisions, including so-called smart televisions, set top boxes, anddigital video recorders. Further, computing devices 402A-402N mayinclude desktop, laptop, or tablet computers, gaming consoles, mobiledevices, including, for example, “smart” phones, cellular telephones,and personal gaming devices.

Television service network 404 is an example of a network configured toenable digital media content, which may include television services, tobe distributed. For example, television service network 404 may includepublic over-the-air television networks, public or subscription-basedsatellite television service provider networks, and public orsubscription-based cable television provider networks and/or over thetop or Internet service providers. It should be noted that although insome examples television service network 404 may primarily be used toenable television services to be provided, television service network404 may also enable other types of data and services to be providedaccording to any combination of the telecommunication protocolsdescribed herein. Further, it should be noted that in some examples,television service network 404 may enable two-way communications betweentelevision service provider site 406 and one or more of computingdevices 402A-402N. Television service network 404 may comprise anycombination of wireless and/or wired communication media. Televisionservice network 404 may include coaxial cables, fiber optic cables,twisted pair cables, wireless transmitters and receivers, routers,switches, repeaters, base stations, or any other equipment that may beuseful to facilitate communications between various devices and sites.Television service network 404 may operate according to a combination ofone or more telecommunication protocols. Telecommunications protocolsmay include proprietary aspects and/or may include standardizedtelecommunication protocols. Examples of standardized telecommunicationsprotocols include DVB standards, ATSC standards, ISDB standards, DTMBstandards, DMB standards, Data Over Cable Service InterfaceSpecification (DOCSIS) standards, HbbTV standards, W3C standards, andUPnP standards.

Referring again to FIG. 4, television service provider site 406 may beconfigured to distribute television service via television servicenetwork 404. For example, television service provider site 406 mayinclude one or more broadcast stations, a cable television provider, ora satellite television provider, or an Internet-based televisionprovider. For example, television service provider site 406 may beconfigured to receive a transmission including television programmingthrough a satellite uplink/downlink. Further, as illustrated in FIG. 4,television service provider site 406 may be in communication with widearea network 408 and may be configured to receive data from contentprovider sites 412A-412N. It should be noted that in some examples,television service provider site 406 may include a television studio andcontent may originate therefrom.

Wide area network 408 may include a packet based network and operateaccording to a combination of one or more telecommunication protocols.Telecommunications protocols may include proprietary aspects and/or mayinclude standardized telecommunication protocols. Examples ofstandardized telecommunications protocols include Global System MobileCommunications (GSM) standards, code division multiple access (CDMA)standards, 3^(rd) Generation Partnership Project (3GPP) standards,European Telecommunications Standards Institute (ETSI) standards,European standards (EN), IP standards, Wireless Application Protocol(WAP) standards, and Institute of Electrical and Electronics Engineers(IEEE) standards, such as, for example, one or more of the IEEE 802standards (e.g., Wi-Fi). Wide area network 408 may comprise anycombination of wireless and/or wired communication media. Wide areanetwork 408 may include coaxial cables, fiber optic cables, twisted paircables, Ethernet cables, wireless transmitters and receivers, routers,switches, repeaters, base stations, or any other equipment that may beuseful to facilitate communications between various devices and sites.In one example, wide area network 408 may include the Internet. Localarea network 410 may include a packet based network and operateaccording to a combination of one or more telecommunication protocols.Local area network 410 may be distinguished from wide area network 408based on levels of access and/or physical infrastructure. For example,local area network 410 may include a secure home network.

Referring again to FIG. 4, content provider sites 412A-412N representexamples of sites that may provide multimedia content to televisionservice provider site 406 and/or computing devices 402A-402N. Forexample, a content provider site may include a studio having one or morestudio content servers configured to provide multimedia files and/orstreams to television service provider site 406. In one example, contentprovider sites 412A-412N may be configured to provide multimedia contentusing the IP suite. For example, a content provider site may beconfigured to provide multimedia content to a receiver device accordingto Real Time Streaming Protocol (RTSP), HTTP, or the like. Further,content provider sites 412A-412N may be configured to provide data,including hypertext based content, and the like, to one or more ofreceiver devices computing devices 402A-402N and/or television serviceprovider site 406 through wide area network 408. Content provider sites412A-412N may include one or more web servers. Data provided by dataprovider site 412A-412N may be defined according to data formats.

Referring again to FIG. 1, source device 102 includes video source 104,video encoder 106, data encapsulator 107, and interface 108. Videosource 104 may include any device configured to capture and/or storevideo data. For example, video source 104 may include a video camera anda storage device operably coupled thereto. Video encoder 106 may includeany device configured to receive video data and generate a compliantbitstream representing the video data. A compliant bitstream may referto a bitstream that a video decoder can receive and reproduce video datatherefrom. Aspects of a compliant bitstream may be defined according toa video coding standard. When generating a compliant bitstream videoencoder 106 may compress video data. Compression may be lossy(discernible or indiscernible to a viewer) or lossless. FIG. 5 is ablock diagram illustrating an example of video encoder 500 that mayimplement the techniques for encoding video data described herein. Itshould be noted that although example video encoder 500 is illustratedas having distinct functional blocks, such an illustration is fordescriptive purposes and does not limit video encoder 500 and/orsub-components thereof to a particular hardware or softwarearchitecture. Functions of video encoder 500 may be realized using anycombination of hardware, firmware, and/or software implementations.

Video encoder 500 may perform intra prediction coding and interprediction coding of picture areas, and, as such, may be referred to asa hybrid video encoder. In the example illustrated in FIG. 5, videoencoder 500 receives source video blocks. In some examples, source videoblocks may include areas of picture that has been divided according to acoding structure. For example, source video data may includemacroblocks, CTUs, CBs, sub-divisions thereof, and/or another equivalentcoding unit. In some examples, video encoder 500 may be configured toperform additional sub-divisions of source video blocks. It should benoted that the techniques described herein are generally applicable tovideo coding, regardless of how source video data is partitioned priorto and/or during encoding. In the example illustrated in FIG. 5, videoencoder 500 includes summer 502, transform coefficient generator 504,coefficient quantization unit 506, inverse quantization and transformcoefficient processing unit 508, summer 510, intra prediction processingunit 512, inter prediction processing unit 514, filter unit 516, andentropy encoding unit 518. As illustrated in FIG. 5, video encoder 500receives source video blocks and outputs a bitstream.

In the example illustrated in FIG. 5, video encoder 500 may generateresidual data by subtracting a predictive video block from a sourcevideo block. The selection of a predictive video block is described indetail below. Summer 502 represents a component configured to performthis subtraction operation. In one example, the subtraction of videoblocks occurs in the pixel domain. Transform coefficient generator 504applies a transform, such as a discrete cosine transform (DCT), adiscrete sine transform (DST), or a conceptually similar transform, tothe residual block or sub-divisions thereof (e.g., four 8×8 transformsmay be applied to a 16×16 array of residual values) to produce a set ofresidual transform coefficients. Transform coefficient generator 504 maybe configured to perform any and all combinations of the transformsincluded in the family of discrete trigonometric transforms, includingapproximations thereof. Transform coefficient generator 504 may outputtransform coefficients to coefficient quantization unit 506. Coefficientquantization unit 506 may be configured to perform quantization of thetransform coefficients. The quantization process may reduce the bitdepth associated with some or all of the coefficients. The degree ofquantization may alter the rate-distortion (i.e., bit-rate vs. qualityof video) of encoded video data. The degree of quantization may bemodified by adjusting a quantization parameter (QP). A quantizationparameter may be determined based on slice level values and/or CU levelvalues (e.g., CU delta QP values). QP data may include any data used todetermine a QP for quantizing a particular set of transformcoefficients. As illustrated in FIG. 5, quantized transform coefficients(which may be referred to as level values) are output to inversequantization and transform coefficient processing unit 508. Inversequantization and transform coefficient processing unit 508 may beconfigured to apply an inverse quantization and an inversetransformation to generate reconstructed residual data. As illustratedin FIG. 5, at summer 510, reconstructed residual data may be added to apredictive video block. In this manner, an encoded video block may bereconstructed and the resulting reconstructed video block may be used toevaluate the encoding quality for a given prediction, transformation,and/or quantization. Video encoder 500 may be configured to performmultiple coding passes (e.g., perform encoding while varying one or moreof a prediction, transformation parameters, and quantizationparameters). The rate-distortion of a bitstream or other systemparameters may be optimized based on evaluation of reconstructed videoblocks. Further, reconstructed video blocks may be stored and used asreference for predicting subsequent blocks.

Referring again to FIG. 5, intra prediction processing unit 512 may beconfigured to select an intra prediction mode for a video block to becoded. Intra prediction processing unit 512 may be configured toevaluate a frame and determine an intra prediction mode to use to encodea current block. As described above, possible intra prediction modes mayinclude planar prediction modes, DC prediction modes, and angularprediction modes. Further, it should be noted that in some examples, aprediction mode for a chroma component may be inferred from a predictionmode for a luma prediction mode. Intra prediction processing unit 512may select an intra prediction mode after performing one or more codingpasses. Further, in one example, intra prediction processing unit 512may select a prediction mode based on a rate-distortion analysis. Asillustrated in FIG. 5, intra prediction processing unit 512 outputsintra prediction data (e.g., syntax elements) to entropy encoding unit518 and transform coefficient generator 504. As described above, atransform performed on residual data may be mode dependent (e.g., asecondary transform matrix may be determined based on a predicationmode).

Referring again to FIG. 5, inter prediction processing unit 514 may beconfigured to perform inter prediction coding for a current video block.Inter prediction processing unit 514 may be configured to receive sourcevideo blocks and calculate a motion vector for PUs of a video block. Amotion vector may indicate the displacement of a PU of a video blockwithin a current video frame relative to a predictive block within areference frame. Inter prediction coding may use one or more referencepictures. Further, motion prediction may be uni-predictive (use onemotion vector) or bi-predictive (use two motion vectors). Interprediction processing unit 514 may be configured to select a predictiveblock by calculating a pixel difference determined by, for example, sumof absolute difference (SAD), sum of square difference (SSD), or otherdifference metrics. As described above, a motion vector may bedetermined and specified according to motion vector prediction. Interprediction processing unit 514 may be configured to perform motionvector prediction, as described above. Inter prediction processing unit514 may be configured to generate a predictive block using the motionprediction data. For example, inter prediction processing unit 514 maylocate a predictive video block within a frame buffer (not shown in FIG.5). It should be noted that inter prediction processing unit 514 mayfurther be configured to apply one or more interpolation filters to areconstructed residual block to calculate sub-integer pixel values foruse in motion estimation. Inter prediction processing unit 514 mayoutput motion prediction data for a calculated motion vector to entropyencoding unit 518.

Referring again to FIG. 5, filter unit 516 receives reconstructed videoblocks and coding parameters and outputs modified reconstructed videodata. Filter unit 516 may be configured to perform deblocking and/orSample Adaptive Offset (SAO) filtering. SAO filtering is a non-linearamplitude mapping that may be used to improve reconstruction by addingan offset to reconstructed video data. It should be noted that asillustrated in FIG. 5, intra prediction processing unit 512 and interprediction processing unit 514 may receive modified reconstructed videoblock via filter unit 216. Entropy encoding unit 518 receives quantizedtransform coefficients and predictive syntax data (i.e., intraprediction data and motion prediction data). It should be noted that insome examples, coefficient quantization unit 506 may perform a scan of amatrix including quantized transform coefficients before thecoefficients are output to entropy encoding unit 518. In other examples,entropy encoding unit 518 may perform a scan. Entropy encoding unit 518may be configured to perform entropy encoding according to one or moreof the techniques described herein. In this manner, video encoder 500represents an example of a device configured to generate encoded videodata according to one or more techniques of this disclose.

Referring again to FIG. 1, data encapsulator 107 may receive encodedvideo data and generate a compliant bitstream, e.g., a sequence of NALunits according to a defined data structure. A device receiving acompliant bitstream can reproduce video data therefrom. Further, asdescribed above, sub-bitstream extraction may refer to a process where adevice receiving a ITU-T H.265 compliant bitstream forms a new ITU-TH.265 compliant bitstream by discarding and/or modifying data in thereceived bitstream. It should be noted that the term conformingbitstream may be used in place of the term compliant bitstream.

As described above, ITU-T H.265 provides where the sequence parameterset syntax includes syntax element log 2_max_pic_order_cnt_lsb_minus4which specifies the value of a variable MaxPicOrderCntLsb. According tothe techniques herein, the sequence parameter set syntax mayadditionally include syntax element log2_max_pic_order_cnt_msb_cycle_minus1 (e.g., immediately preceding orfollowing log 2_max_pic_order_cnt_lsb_minus4 or in some other locationin the sequence parameter set or another parameter set). In one example,log 2_max_pic_order_cnt_msb_cycle_minus1 may be based on the followingdefinition:

-   -   log 2_max_pic_order_cnt_msb_cycle_minus1 specifies the value of        the variable MaxPicOrderCntMSBCycle that is used in the decoding        process for picture order count as follows:        MaxPicOrderCntMSBCycle=2^((log2_max_pic_order_cnt_msb_cycle_minus1+1))    -   The value of log 2_max_pic_order_cnt_msb_cycle_minus1 shall be        in the range of 0 to 15, inclusive.

It should be noted that in some examples, the value of log2_max_pic_order_cnt_msb_cycle_minus1 may be within other ranges (e.g., 0to 16, inclusive, 0 to 28, inclusive, 0 to 48, inclusive, etc.).

In one example, a slice header may include slice_poc_info( ) syntax. Forexample, Table 3 illustrates an example of a slice header includingslice_poc_info( ) syntax. The syntax elements included in slice_header() may be based on the definitions provided above.

TABLE 3 Descriptor slice_header( ) {  slice_pic_parameter_set_id ue(v) slice_address u(v)  slice_type ue(v)  if ( slice_type != I )  log2_diff_ctu_max_bt_size ue(v)   slice_poc_info( )  byte_alignment( )}

Table 4 provides an example of syntax for slice_poc_info( ).

TABLE 4 Descriptor slice_poc_info( ) {  slice_pic_order_cnt_lsb u(v)  slice_pic_order_cnt_msb_cycle_present u(1) if(slice_pic_order_cNt_msb_cycle_present) {     slice_pic_order_cnt_msb_cycle u(v)      } }

Syntax elements slice_pic_order_cnt_lsb,slice_pic_order_cnt_msb_cycle_present, and slice_pic_order_cnt_msb_cyclein Table 4 may be based on the following example definitions:

-   -   slice_pic_order_cnt_lsb specifies the picture order count modulo        MaxPicOrderCntLsb for the current picture. The length of the        slice_pic_order_cnt_lsb syntax element is log        2_max_pic_order_cnt_lsb_minus4+4 bits. The value of the        slice_pic_order_cnt_lsb shall be in the range of 0 to        MaxPicOrderCntLsb−1, inclusive.    -   slice_pic_order_cnt_msb_cycle_present equal to 1 indicates that        slice_pic_order_cnt_msb_cycle syntax element follows next.        slice_pic_order_cnt_msb_cycle_present equal to 0 indicates that        slice_pic_order_cnt_msb_cycle syntax element is not signaled.        When not signaled slice_pic_order_cnt_msb_cycle_present is        inferred to be equal to 0. When current picture is an IDR        picture the slice_pic_order_cnt_msb_cycle_present shall be equal        to 0.    -   slice_pic_order_cnt_msb_cycle specifies the picture order count        MSB cycle value. The length of the slice_pic_order_cnt_msb_cycle        syntax element is log 2_max_pic_order_cnt_msb_cycle_minus1+1        bits. The value of the slice_pic_order_cnt_msb_cycle shall be in        the range of 0 to MaxPicOrderCntMSBCycle−1, inclusive.

It should be noted that in some examples, slice_pic_order_cnt_msb_cyclemay be coded as i(v) to allow signaling of negative values forslice_pic_order_cnt_msb_cycle.

It should be noted that in some examples, minus one signaling may not beused for log 2_max_pic_order_cnt_msb_cycle_minus1. That is, log2_max_pic_order_cnt_msb_cycle_minus1 may be replaced with syntax elementlog 2_max_pic_order_cnt_msb_cycle, which may be based on the followingdefinition:

-   -   log 2_max_pic_order_cnt_msb_cycle specifies the value of the        variable    -   MaxPicOrderCntMSBCycle that is used in the decoding process for        picture order count as follows:        MaxPicOrderCntMSBCycle=2^((log2_max_pic_order_cnt_msb_cycle))    -   The value of log 2_max_pic_order_cnt_msb_cycle shall be in the        range of 0 to 16 (or 0 to 15, inclusive, 0 to 28, inclusive, 0        to 48, inclusive, etc), inclusive.

When log 2_max_pic_order_cnt_msb_cycle is used the definition ofslice_pic_order_cnt_msb_cycle may be modified as follows:

-   -   slice_pic_order_cnt_msb_cycle specifies the picture order count        MSB cycle value. The length of the slice_pic_order_cnt_msb_cycle        syntax element is log 2_max_pic_order_cnt_msb_cycle bits. The        value of the slice_pic_order_cnt_msb_cycle shall be in the range        of 0 to MaxPicOrderCntMSBCycle−1, inclusive.

It should be noted that in some examples, log2_max_pic_order_cnt_msb_cycle_minus1 may not be used and in such casesslice_pic_order_cnt_msb_cycle may be signaled using a ue(v) data typeinstead of a u(v) data type.

In one example, instead of signaling log2_max_pic_order_cnt_msb_cycle_minus1, the value ofMaxPicOrderCntMSBCycle may be derived from the value of log2_max_pic_order_cnt_lsb_minus4 and MaxPicOrderCnt, which is pre-defined.In one example, MaxPicOrderCntMSBCycle may be derived as follows:PicOrderCntBitDepth=Ceil(Log 2(MaxPicOrderCnt))Log 2MaxPicOrderCntMSBCycle=PicOrderCntBitDepth−(log2_max_pic_order_cnt_lsb_minus4+4)MaxPicOrderCntMSBCycle=2^(Log2MaxPicOrderCntMSBCycle)

In one example, instead of signaling log 2_max_pic_order_cnt_lsb_minus4,the value of MaxPicOrderCntLsb may be derived from the value of log2_max_pic_order_cnt_msb_cycle_minus1 and MaxPicOrderCnt, which ispre-defined. In one example, MaxPicOrderCntLsb may be derived asfollows:PicOrderCntBitDepth=Ceil(Log 2(MaxPicOrderCnt))Log 2MaxPicOrderCntLSB=PicOrderCntBitDepth−(log2_max_pic_order_cnt_msb_cycle_minus1+1)MaxPicOrderCntLsb=2^(Log2MaxPicOlderCntLSB)

According to the syntax elements provided in slice_poc_info( ), aPicOrderCntVal being equal to PicOrderCntMsb+slice_pic_order_cnt_lsb maybe derived as follows:

-   -   When the current picture is not an IDR picture or the current        picture does not have slice_pic_order_cnt_msb_cycle signaled,        the variables prevPicOrderCntLsb and prevPicOrderCntMsb are        derived as follows:        -   Let prevTid0Pic be the previous picture in decoding order            that has TemporalId equal to 0 and a sub-layer non-reference            picture.        -   The variable prevPicOrderCntLsb is set equal to            slice_pic_order_cnt_lsb of prevTid0Pic.        -   The variable prevPicOrderCntMsb is set equal to            PicOrderCntMsb of prevTid0Pic.    -   The variable PicOrderCntMsb of the current picture is derived as        follows:        -   If the current picture is an TDR picture or if log            2_max_pic_order_cnt_msb_cycle for the active SPS for this            slice is present and is equal to 0 the variable            PicOrderCntMsb is set equal to 0.        -   Otherwise if the slice of the current picture has            slice_pic_order_cnt_msb_cycle signaled, the variable            PicOrderCntMSB is set equal to slice_pic_order_cnt_msb_cycle            multiplied by MaxPicOrderCntLsb.        -   Otherwise, PicOrderCntMsb is derived as follows:    -   if((slice_pic_order_cnt_lsb<prevPicOrderCntLsb) &&        ((prevPicOrderCntLsb−slice_pic_order_cnt_lsb)>=(MaxPicOrderCntLsb/2)))        -   PicOrderCntMsb=prevPicOrderCntMsb MaxPicOrderCntLsb    -   else if((slice_pic_order_cnt_lsb>prevPicOrderCntLsb) &&        ((slice_pic_order_cnt_lsb−prevPicOrderCntLsb)>(MaxPicOrderCntLsb/2)))        -   PicOrderCntMsb=prevPicOrderCntMsb−MaxPicOrderCntLsb    -   else    -   PicOrderCntMsb=prevPicOrderCntMsb        PicOrderCntVal is derived as follows:        PicOrderCntVal=PicOrderCntMsb+slice_pic_order_cnt_lsb    -   It should be noted that in some examples, the value of        PicOrderCntVal shall be in the range of −2³¹ to 2³¹⁻¹,        inclusive.

In another example, a PicOrderCntVal being equal tocurrentPicOrderCntMsb+slice_pic_order_cnt_lsb may be derived as follows:

-   -   If the current picture is an IDR picture the variable        currentPicOrderCntMsb is set equal to 0.    -   Otherwise if the slice of the current picture has        slice_pic_order_cnt_msb_cycle signaled, the variable        currentPicOrderCntMsb is set equal to        slice_pic_order_cnt_msb_cycle multiplied by MaxPicOrderCntLsb.    -   Otherwise, the variable currentPicOrderCntMSB is derived as        follows:        -   Let prevPOCMSBPic be the previous picture in decoding order            that has slice_pic_order_cnt_msb_cycle signaled or is an IDR            picture, whichever is closer in decoding order to the            current picture.        -   Then the variable currentPicOrderCntMsb is set equal to 0 if            prevPOCMSBPic is an IDR picture or is set equal to            slice_pic_order_cnt_msb_cycle of the prevPOCMSBPic picture            multiplied by MaxPicOrderCntLsb if prevPOCMSBPic is not an            IDR picture.    -   PicOrderCntVal is derived as follows:        PicOrderCntVal=PicOrderCntMsb+slice_pic_order_cnt_lsb

In one example, a flag to control signaling of slice level MSB pictureorder count related syntax elements may be signaled in a parameter set,e.g., a VPS, an SPS, or a PPS. Table 5 illustrates an example of asequence parameter set includingslice_pic_order_cnt_msb_signaling_present.

TABLE 5 Descriptor seq_parameter_set_rbsp( ) { ... log2_max_pic_order_cnt_lsb_minus4 ue(v)  slice_pic_order_cnt_msb_signaling_present u(1)  if(slice_pic_order_cnt_msb_signaling_present)  log2_max_pic_order_cnt_msb_cycle ue(v)  rbsp_trailing_bits( ) }

With respect to Table 5 the semantics of various syntax elements may beas follows:

-   -   log 2_max_pic_order_cnt_lsb_minus4 specifies the value of the        variable MaxPicOrderCntLsb that is used in the decoding process        for picture order count as follows:        MaxPicOrderCntLsb=2^((log2_max_pic_order_cnt_lsb_minus4+4))    -   The value of log 2_max_pic_order_cnt_lsb_minus4 shall be in the        range of 0 to 12, inclusive.    -   In another example, the value of log        2_max_pic_order_cnt_lsb_minus4 shall be in the range of 0 to 16,        inclusive. In general, some other valid value range may be        declared for log 2_max_pic_order_cnt_lsb_minus4.    -   slice_pic_order_cnt_msb_signaling_present equal to 0 indicates        that POC MSB related information for picture order count is not        signaled in the slice header.        slice_pic_order_cnt_msb_signaling_present equal to 1 indicates        that POC MSB related information may be signaled in the slice        header.    -   log 2_max_pic_order_cnt_msb_cycle specifies the value of the        variable MaxPicOrderCntMSBCycle as follows:        MaxPicOrderCntMSBCycle=2^((log2_max_pic_order_cnt_msb_cycle))    -   The value of log 2_max_pic_order_cnt_msb_cycle shall be in the        range of 0 to 28, inclusive.    -   In another example, the value of log        2_max_pic_order_cnt_msb_cycle shall be in the range of 0 to 16,        inclusive. In general, some other valid value range may be        declared for log 2_max_pic_order_cnt_msb_cycle.

When syntax element slice_pic_order_cnt_msb_signaling_present isincluded in a parameter set, slice_poc_info( ) may be as illustrated inTable 6.

TABLE 6 Descriptor slice_poc_info( ) {  slice_pic_order_cnt_lsb u(v)  if(slice_pic_order_cnt_msb_signaling_present) {    slice_pic_order_cnt_msb_cycle_present u(1)   if(slice_pic_order_cnt_msb_cycle_present) {      slice_pic_order_ent_msb_cycle u(v) or ue(v)      }   } }

With respect to Table 6 the semantics of various syntax elements may beas follows:

-   -   slice_pic_order_cnt_lsb specifies the picture order count modulo        MaxPicOrderCntLsb for the current picture. The length of the        slice_pic_order_cnt_lsb syntax element is log        2_max_pic_order_cnt_lsb_minus4+4 bits. The value of the        slice_pic_order_cnt_lsb shall be in the range of 0 to        MaxPicOrderCntLsb−1, inclusive.

In the case of the example illustrated with respect to Table 5 and Table6 slice_pic_order_cnt_msb_cycle_present andslice_pic_order_cnt_msb_cycle may be based on the following definition:

-   -   slice_pic_order_cnt_msb_cycle_present equal to 1 indicates that        slice_pic_order_cnt_msb_cycle syntax element follows next.        slice_pic_order_cnt_msb_cycle_present equal to 0 indicates that        slice_pic_order_cnt_msb_cycle syntax element is not signaled.        When not signaled slice_pic_order_cnt_msb_cycle_present is        inferred to be equal to 0. When current picture is an IDR        picture the slice_pic_order_cnt_msb_cycle_present shall be equal        to 0. When log 2_max_pic_order_cnt_msb_cycle is equal to 0,        slice_pic order cnt msb cycle present shall be equal to 0.    -   slice_pic_order_cnt_msb_cycle specifies the picture order count        MSB cycle value. The length of the slice_pic_order_cnt_msb_cycle        syntax element is log 2_max_pic_order_cnt_msbcycle bits. The        value of the slice_pic_order_cnt_msb_cycle shall be in the range        of 0 to MaxPicOrderCntMSBCycle−1, inclusive.

In one example, slice_pic_order_cnt_msb_cycle_present may be included ina parameter set. When syntax elementslice_pic_order_cnt_msb_cycle_present is included in a parameter set,slice_poc_info( ) may be modified as illustrated in Table 7.

TABLE 7 Descriptor slice_poc_info( ) {  slice_pic_order_cnt_lsb u(v) if(slice_pic_order_cnt_msb_cycle_present) {    slice_pic_order_cnt_msb_cycle u(v) or ue(v)      } }

In some examples, the presence of syntax elements in slice_poc_info( )may be based on values of log 2_max_pic_order_cnt_msb_cycle_minus1 orlog 2_max_pic_order_cnt_msb_cycle. For example, Table 8 illustrates aexample, where the presence of slice_pic_order_cnt_msb_cycle_present andslice_pic_order_cnt_msb_cycle are conditioned on log2_max_pic_order_cnt_msb_cycle not being equal to zero. In one example,if log 2_max_pic_order_cnt_msb_cycle is equal to zero,slice_pic_order_cnt_msb_cycle_present shall be constrained to be equalto zero.

TABLE 8 Descriptor slice_poc_info( ) {  slice_pic_order_cnt_lsb u(v)  if(slice_pic_order_ent_msb_signaling_present &&log2_max_pic_order_cnt_msb_cycle!=0) {   slice_pic_order_cnt_msb_cycle_present u(1) if(slice_pie_order_ent_msb_cycle_present) {    slice_pic_order_cnt_msb_cycle ue(v)      }   } }

In one example instead of signaling slice_pic_order_cnt_msb_cycle, asyntax element slice_pic_order_msb value may be signaled. The syntaxelement slice_pic_order_msb may be coded as ue(v) or as u(v). In thiscase, instead of log 2_max_pic_order_cnt_msb_cycle_minus1, a syntaxelement log 2_max_pic_order_cnt_msb_minus1 may be signaled withsemantics as follows:

-   -   log 2_max_pic_order_cnt_msb_minus1 specifies the value of the        variable MaxPicOrderCntMSB that is used in the decoding process        for picture order count as follows:        MaxPicOrderCntMSB=2^((log2_max_pic_order_cnt_msb_minus1+1))

In some examples, constraint may be put on MaxPicOrderCntMSB. Further,in this case, the decoding process for picture order count may bemodified such that, the variable PicOrderCntMSB is set equal toslice_pic_order_msb.

In one example slice_pic_order_cnt_msb_cycle may be always signaled whenslice_pic_order_cnt_lsb is equal to zero. In one example, this may befurther controlled by an additional slice and/or parameter set levelflag(s). In other cases, a constraint may be imposed for whetherslice_pic_order_cnt_msb_cycle is signaled and possible values thereof.In another example, slice_pic_order_cnt_msb_cycle may be always signaledfor a TId 0 picture. In one example, constraints may be placed onvarious syntax elements and/or across slices and/or parameters sets.

In one example, a sequence parameter set may include a flag to indicatewhether a syntax element slice_pic_order_cnt is present in a sliceheader. slice_pic_order_cnt may specify the value of picture order countvalue without separating bits to MSB and LSB and may be based on thefollowing definition.

-   -   slice_pic_order_cnt specifies the picture order count value for        the current picture. The value of the slice_pic_order_cnt shall        be in the range of 0 to MaxPicOrderCnt, inclusive.

Table 9 and Table 10 illustrate an example where a flag,full_pic_order_cnt_signal_flag, indicates whether log2_max_pic_order_cnt_lsb_minus4 and log2_max_pic_order_cnt_msb_cycle_minus1 are present in a sequence parameterset and whether a syntax element slice_pic_order_cnt is present in aslice header.

TABLE 9 Descriptor seq_parameter_set_rbsp( ) { ...  full_pic_order_cnt_signal_flag u(1)   if( !full_pic_order_ent_sigial_flag) {   log2_max_pic_order_cnt_lsb_minus4ue(v)   log2_max_pic_order_cnt_msb_cycle_minus1 ue(v)  } rbsp_trailing_bits( ) }

TABLE 10 Descriptor slice_poc_info( ) {  if(full_pic_order_cnt_signal_flag) {   slice_pic_order_cnt  }  else {  slice_pic_order_cnt_lsb u(v)  if(slice_pic_order_cnt_msb_cycle_present) {     slice_pic_order_cnt_msb_cycle uc(v)  } }

In the case of the example illustrated with respect to Table 9 and Table10, PicOrderCntVal may be derived as follows:

-   -   if (full_pic_order_cnt_signal_flag)        -   PicOrderCntVal=slice_pic_order_cnt    -   else    -   PicOrderCntVal=PicOrderCntMsb+slice_pic_order_cnt_lsb

In the case of the example illustrated with respect to Table 5 and Table6, PicOrderCntVal may be derived as follows:

-   -   When the current picture is not an IRAP picture or the current        picture does not have slice_pic_order_cnt_msb_cycle signalled,        the variables prevPicOrderCntLsb and prevPicOrderCntMsb are        derived as follows:        -   Let prevTid0Pic be the previous picture in decoding order            that has TemporalId equal to 0        -   The variable prevPicOrderCntLsb is set equal to            slice_pic_order_cnt_lsb of prevTid0Pic.        -   The variable prevPicOrderCntMsb is set equal to            PicOrderCntMsb of prevTid0Pic.    -   The variable PicOrderCntMsb of the current picture is derived as        follows:        -   If the current picture is an IRAP picture or if log            2_max_pic_order_cnt_msb_cycle for the active SPS for this            slice is present and is equal to 0 the variable            PicOrderCntMsb is set equal to 0.        -   Otherwise if the slice of the current picture has            slice_pic_order_cnt_msb_cycle signalled, the variable            PicOrderCntMSB is set equal to slice_pic_order_cnt_msb_cycle            multiplied by MaxPicOrderCntLsb.        -   Otherwise, PicOrderCntMsb is derived as follows:            -   if((slice_pic_order_cnt_lsb<prevPicOrderCntLsb) &&                ((prevPicOrderCntLsb−slice_pic_order_cnt_lsb)>=(MaxPicOrderCntLsb/2)))                -   PicOrderCntMsb=prevPicOrderCntMsb+MaxPicOrderCntLsb            -   else if((slice_pic_order_cnt_lsb>prevPicOrderCntLsb) &&                ((slice_pic_order_cnt_lsb−prevPicOrderCntLsb)>(MaxPicOrderCntLsb/2)))                -   PicOrderCntMsb=prevPicOrderCntMsb−MaxPicOrderCntLsb            -   else                -   PicOrderCntMsb=prevPicOrderCntMsb    -   PicOrderCntVal is derived as follows:        PicOrderCntVal=PicOrderCntMsb+slice_pic_order_cnt_lsb    -   If slice_pic_order_cnt_msb_signaling_present is equal to 1 the        value of PicOrderCntVal shall be in the range of        −2^((log2_max_pic_order_cnt_lsb_minus4+log2_max_pic_order_cnt_msb_cycle+3))        to        2^((log2_max_pic_order_cnt_lsb_minus4+log2_max_pic_order_cnt_msb_cycle+3))−1,        inclusive.    -   Otherwise, the value of PicOrderCntVal shall be in the range of        −2³¹ to 2³¹−1, inclusive.

In another example, if in a coded video sequence ifslice_pic_order_cnt_msb_cycle is ever signalled, the value ofPicOrderCntVal shall be in the range of−2^((log2_max_pic_order_cnt_lsb_minus4+log2_max_pic_order_cnt_msb_cycle+3))to2^((log2_max_pic_order_cnt_lsb_minus4+log2_max_pic_order_cnt_msb_cycle+3))−1,inclusive.

Otherwise the value of PicOrderCntVal shall be in the range of −2³¹ to2³¹−1, inclusive.

In yet another example, the otherwise part of the statements above mayuse a different value than the value of 2³¹. For example, the 2³¹ may bereplaced in the otherwise part above with some other value such as 2⁴⁸or 2⁶⁴ or 2¹⁶ etc.

Further, in one example, an Instantaneous decoding refresh (IDR) picturemay be described as an IRAP picture which does not refer to any picturesother than itself for inter prediction in its decoding process and isthe first picture of a coded video sequence in decoding order.

As described above, a picture may be partitioned into slices and/ortiles, where a slice includes a sequence of CTUs in raster scan orderand where a tile is a sequence of CTUs corresponding to a rectangulararea of a picture. As described above, a slice may include one or moretiles. Further, there may be cases where the same grouping of CTUs(i.e., a group CTUs covering a rectangular area of a picture) may beclassified as a slice or as a tile. “Tiles groups for VVC,” 12^(th)Meeting of ISO/IEC JTC1/SC29/WG11 3-12 Oct. 2018, Macao, CN, documentJVET-L0415-v1, which is referred to herein as JVET-L0415, describeswhere slices are required to consist of an integer number of completetiles instead of consisting of an integer number of complete CTUs. Assuch, in JVET-L0415, the raster-scan CTU slices, which are not arectangular region of a picture, are no longer supported and the nameslice is changed to tile group. JVET-L0415 retains the structure of aslice header, but refers to it as a tile group header, replaces sliceaddress with a tile group address in the tile group header, adds asyntax element num_tiles_in_tile_group that specifies the number oftiles in a tile group, and removes the end_of_slice_flag syntax element,instead the end of the tile group is given by the tile group address andnum_tiles_in_tile_group. Although the techniques described herein aredescribed above with respect to slices, the techniques described hereinare applicable to cases where a slice is restricted to consist of aninteger number of complete tiles. That is, the techniques describedherein for indicating a picture order count value may be incorporated into techniques where a slice includes tile groups.

For example, Table 11 and Table 12 illustrate an examples of a tilegroup header syntax indicating a picture order count value according tothe techniques herein.

TABLE 11 Descriptor tile_group_header( ) { tile_group_pic_parameter_set_id ue(v)  tile_group_pic_order_cnt_lsbu(v)  if(NumTilesInPic > 1) {   tile_group_address u(v)   num_tiles_in_tile_group_minus1 ue(v)  }  tile_group_type ue(v)  if (tile_group_type != I) {   log2_diff_ctu_max_bt_size ue(v)   if(sps_sbtmvp_enabled_flag ) {    sbtmvp_size_override_flag u(1)    if(sbtmvp_size_override_flag )     log2_sbtmvp_active_size_minus2 u(3)   }  if( sps_temporal_mvp_enabled_flag )   tile_group_temporal_mvp_enabled_flag u(1)   if( tile_group_type == B)   mvd_l1_zero_flag u(1)   if( tile_group_temporal_mvp_enabled_flag ) {   if( tile_group_type == B)     collocated_from_l0_flag u(1)   }  six_minus_max_num_merge_cand ue(v)  }  dep_quant_enabled_flag u(1) if( !dep_quant_enabled_flag )   sign_data_hiding_enabled_flag u(1)  if(num_tiles_in_tile_group_minus1 > 0) {   offset_len_minus1 ue(v)   for( i= 0; i < num_tiles_in_tile_group_minus1; i++)   entry_point_offset_minus1[ i ] u(v)  }  byte_alignment( ) }

TABLE 12 Descriptor tile_group_header( ) {  tile_group_pic_parameter_setid ue(v)  if(NumTilesInPic > 1 ) {   tile_group_address u(v)   num_tiles_in_tile_group_minus1 ue(v)  }  tile_group_type ue(v) tile_group_pic_order_cnt_lsb u(v)  if( tile_group_type != I ) {  log2_diff_ctu_max_bt_size ue(v)   if( sps_sbtmvp_enabled_flag ) {   sbtmvp_size_override_flag u(1)    if( sbtmvp_size_override_flag )    log2_sbtmvp_active_size_minus2 u(3)   }   if(sps_temporal_mvp_enabled_flag )    tile_group_temporal_mvp_cnabled_flagu(1)   if( tile_group_type == B)    mvd_l1_zero_flag u(1)   if(tile_group_temporal_mvp_enabled_flag ) {    if( tile_group_type == B)    collocated_from_l0_flag u(1)   }   six_minus_max_num_merge_candue(v)  }  dep_quant_enabled_flag u(1)  if( !dep_quant_enabled_flag )  sign_data_hiding_enabled_flag u(1)  if(num_tiles_in_tile_group_minus1 > 0) {   offset_len_minus1 ue(v)   for( i= 0; i < num_tiles_in_tile_group_minus1; i++)    entry_point_offset_minus1[ i ] u(v)  }  byte_alignment( ) }

With respect to Tables 11 and 12, the semantics of various syntaxelements may be as follows:

-   -   When present, the value of the tile group header syntax element        tile_group_pic_parameter_set_id shall be the same in all tile        group headers of a coded picture.    -   tile_group_pic_parameter_set_id specifies the value of        pps_pic_parameter_set_id for the PPS in use. The value of        tile_group_pic_parameter_set_id shall be in the range of 0 to        63, inclusive.    -   tile_group_pic_order_cnt_lsb specifies the picture order count        modulo MaxPicOrderCntLsb for the current picture. The length of        the tile_group_pic_order_cnt_lsb syntax element is log 2        max_pic_order_cnt_lsb_minus4+4 bits. The value of the        tile_group_pic_order_cnt_lsb shall be in the range of 0 to        MaxPicOrderCntLsb−1, inclusive.    -   In another example:    -   tile_group_pic_order_cnt_lsb specifies the picture order count        modulo MaxPicOrderCntLsb for the picture this tile group belongs        to. The length of the tile_group_pic_order_cnt_lsb syntax        element is log 2_max_pic_order_cnt_lsb_minus4+4 bits. The value        of the tile_group_pic_order_cnt_lsb shall be in the range of 0        to MaxPicOrderCntLsb−1, inclusive.    -   In another example, tile_group_pic_order_cntl_lsb syntax element        may be called some other name. For example        tile_group_pic_order_cnt_lsb may be called pic_order_cnt_lsb. Or        tile_group_pic_order_cnt_lsb may be called        tile_set_pic_order_cnt_lsb. Or some other name may be used for        tile_group_pic_order_cnt_lsb.    -   tile_group_address specifies the tile address of the first tile        in the tile group. The length of tile_group_address is Ceil(Log        2 (NumTilesInPic)) bits. The value of tile_group_address shall        be in the range of 0 to NumTileslnPic−1, inclusive, and the        value of tile_group_address shall not be equal to the value of        tile_group_address of any other coded tile group NAL unit of the        same coded picture. When tile_group_address is not present it is        inferred to be equal to 0.    -   num_tiles_in_tile_group_minus1 plus 1 specifies the number of        tiles in the tile group. The value of        num_tiles_in_tile_group_minus1 shall be in the range of 0 to        NumTilesInPic−1, inclusive. When not present, the value of        num_tiles_in_tile_group_minus1 is inferred to be equal to 0.    -   tile_group_type specifies the coding type of the tile group        according to Table 13.

TABLE 13 Name of tile_group_type tile_group_type 0 B (B tile group) 1 P(P tile group) 2 I (I tile group)

-   -   When nal_unit_type is equal to IRAP NUT, i.e., the picture is an        IRAP picture, tile_group_type shall be equal to 2.    -   log 2_diff_ctu_max_bt_size specifies the difference between the        luma CTB size and the maximum luma size (width or height) of a        coding block that can be split using a binary split. The value        of log 2_diff_ctu_max_bt_size shall be in the range of 0 to        CtbLog2SizeY−MinCbLog2SizeY, inclusive.    -   When log 2_diff_ctu_max_bt_size is not present, the value of log        2_diff_ctu_max_bt_size is inferred to be equal to 2.    -   The variables MinQtLog2SizeY, MaxBtLog2SizeY, MinBtLog2SizeY,        MaxTtLog2SizeY, MinTtLog2SizeY, MaxBtSizeY, MinBtSizeY,        MaxTtSizeY, MinTtSizeY and MaxMttDepth are derived as follows:    -   MinQtLog2SizeY=(tile_group_type==I)? MinQtLog2SizeIntraY:        MinQtLog2SizeInterY    -   MaxBtLog2SizeY=CtbLog2SizeY−log 2_diff_ctu_max_bt_size    -   MinBtLog2SizeY=MinCbLog2SizeY    -   MaxTtLog2SizeY=(tile_group_type==I)? 5:6    -   MinTtLog2SizeY=MinCbLog2SizeY    -   MinQtSizeY=1<<MinQtLog2SizeY    -   MaxBtSizeY=1<<MaxBtLog2SizeY    -   MinBtSizeY=1<<MinBtLog2SizeY    -   MaxTtSizeY=1<<MaxTtLog2SizeY    -   MinTtSizeY=1<<MinTtLog2SizeY    -   MaxMttDepth=(tile_group_type==I)?    -   max_mtt_hierarchy_depth_intra_tile_groups:        max_mtt_hierarchy_depth_inter_tile_groups    -   sbtmvp_size_override_flag equal to 1 specifies that the syntax        element log 2_sbtmvp_active_sizeminus2 is present for the        current tile group. sbtmvp_size_override_flag equal to 0        specifies that the syntax element log 2_atmvp_active_sizeminus2        is not present and log 2_sbtmvp_size_activeminus2 is inferred to        be equal to log 2_sbtmvp_default_sizeminus2.

log 2_sbtmvp_active_size_minus2 plus 2 specifies the value of thesubblock size that is used for deriving the motion parameters for thesubblock-based TMVP of the current tile group. When log2_sbtmvp_size_active_minus2 is not present, it is inferred to be equalto log 2_sbtmvp_default_size_minus2. The variable is derived as follows:Log 2SbtmvpSize=log 2_sbtmvp_size_active_minus2+2

-   -   tile_group_temporal_mvp_enabled_flag specifies whether temporal        motion vector predictors can be used for inter prediction. If        tile_group_temporal_mvp_enabled_flag is equal to 0, the syntax        elements of the current picture shall be constrained such that        no temporal motion vector predictor is used in decoding of the        current picture. Otherwise (tile_group_temporal_mvp_enabled_flag        is equal to 1), temporal motion vector predictors may be used in        decoding of the current picture. When not present, the value of        tile_group_temporal_mvp_enabled_flag is inferred to be equal to        0.    -   mvd_l1_zero_flag equal to 1 indicates that the mvd_coding(x0,        y0, 1) syntax structure is not parsed and MvdL1[x0][y0][compIdx]        is set equal to 0 for compIdx=0 . . . 1. mvd_l1_zero_flag equal        to 0 indicates that the mvd_coding(x0, y0, 1) syntax structure        is parsed.    -   collocated_from_l0_flag equal to 1 specifies that the collocated        picture used for temporal motion vector prediction is derived        from reference picture list 0. collocated_from_l0_flag equal to        0 specifies that the collocated picture used for temporal motion        vector prediction is derived from reference picture list 1. When        collocated_from_l0_flag is not present, it is inferred to be        equal to 1.    -   six_minus_max_num_merge_cand specifies the maximum number of        merging motion vector prediction (MVP) candidates supported in        the tile group subtracted from 6. The maximum number of merging        MVP candidates, MaxNumMergeCand is derived as follows:        MaxNumMergeCand=6−six_minus_max_num_merge_cand    -   The value of MaxNumMergeCand shall be in the range of 1 to 6,        inclusive.    -   dep_quant_enabled_flag equal to 0 specifies that dependent        quantization is disabled. dep_quant_enabled_flag equal to 1        specifies that dependent quantization is enabled.    -   sign_data_hiding_enabled_flag equal to 0 specifies that sign bit        hiding is disabled. sign_data_hiding_enabled_flag equal to 1        specifies that sign bit hiding is enabled. When        sign_data_hiding_enabled_flag is not present, it is inferred to        be equal to 0.    -   offset_len_minus1 plus 1 specifies the length, in bits, of the        entry_point_offset_minus1[i] syntax elements. The value of        offset_len_minus1 shall be in the range of 0 to 31, inclusive.    -   entry_point_offset_minus1[i] plus 1 specifies the i-th entry        point offset in bytes, and is represented by offset_len_minus1        plus 1 bits. The tile group data that follow the tile group        header consists of num_tiles_in_tile_group_minus1+1 subsets,        with subset index values ranging from 0 to        num_tiles_in_tile_group_minus1, inclusive. The first byte of the        tile group data is considered byte 0. When present, emulation        prevention bytes that appear in the tile group data portion of        the coded tile group NAL unit are counted as part of the tile        group data for purposes of subset identification. Subset 0        consists of bytes 0 to entry_point_offset_minus1[0], inclusive,        of the coded tile group data, subset k, with k in the range of 1        to num_tiles_in_tile_group_minus1−1, inclusive, consists of        bytes firstByte[k] to lastByte[k], inclusive, of the coded tile        group data with firstByte[k] and lastByte[k] defined as:

${{firstByte}\lbrack k\rbrack} = {\sum\limits_{n = 1}^{k}( {{{entry\_ point}{\_ offset}{{\_ minus1}\lbrack {n - 1} \rbrack}} + 1} )}$lastByte[k] = firstByte[k] + entry_point_offset_minus1[k]

-   -   The last subset (with subset index equal to        num_tiles_in_tile_group_minus1) consists of the remaining bytes        of the coded tile group data,    -   Each subset shall consist of all coded bits of all CTUs in the        tile group that are within the same tile.

In the case of the example illustrated with respect to Table 11 andTable 12, PicOrderCntVal may be derived as follows:

-   -   Output of this process is PicOrderCntVal, the picture order        count of the current picture. Each coded picture is associated        with a picture order count variable, denoted as PicOrderCntVal.    -   In another example:    -   Each tile group is associated with a picture order count        variable, denoted as PicOrderCntVal.    -   In another example:    -   Each tile group of a coded picture is associated with a picture        order count variable, denoted as PicOrderCntVal.    -   When the current picture is not an IRAP picture, the variables        prevPicOrderCntLsb and prevPicOrderCntMsb are derived as        follows:        -   Let prevTid0Pic be the previous picture in decoding order            that has TemporalId equal to 0.        -   The variable prevPicOrderCntLsb is set equal to            tile_group_pic_order_cnt_lsb of prevTid0Pic.        -   The variable prevPicOrderCntMsb is set equal to            PicOrderCntMsb of prevTid0Pic.            -   The variable PicOrderCntMsb of the current picture is                derived as follows:        -   If the current picture is an IRAP picture, PicOrderCntMsb is            set equal to 0.        -   Otherwise, PicOrderCntMsb is derived as follows:            -   if((tile_group_pic_order_cnt_lsb<prevPicOrderCntLsb) &&                ((prevPicOrderCntLsb−tile_group_pic_order_cnt_lsb)>=(MaxPicOrderCntLsb/2)))                -   PicOrderCntMsb=prevPicOrderCntMsb+MaxPicOrderCntLsb            -   else                if((tile_group_pic_order_cnt_lsb>prevPicOrderCntLsb) &&                ((tile_group_pic_order_cnt_lsb−prevPicOrderCntLsb)>(MaxPicOrderCntLsb/2)))                -   PicOrderCntMsb=prevPicOrderCntMsb−MaxPicOrderCntLsb            -   else                -   PicOrderCntMsb=prevPicOrderCntMsb    -   PicOrderCntVal is derived as follows:        PicOrderCntVal=PicOrderCntMsb+tile_group_pic_order_cnt_lsb    -   The value of PicOrderCntVal shall be in the range of −2³¹ to        2³¹−1, inclusive.    -   In one CVS, the PicOrderCntVal values for any two coded pictures        shall not be the same.    -   The function PicOrderCnt(picX) is specified as follows:        PicOrderCnt(picX)=PicOrderCntVal of the picture picX    -   The function DiffPicOrderCnt(picA, picB) is specified as        follows:        DiffPicOrderCnt(picA,picB)=PicOrderCnt(picA)−PicOrderCnt(picB)    -   The bitstream shall not contain data that result in values of    -   DiffPicOrderCnt(picA, picB) used in the decoding process that        are not in the range of −2¹⁵ to 2¹⁵−1, inclusive.        -   NOTE 2—Let X be the current picture and Y and Z be two other            pictures in the same CVS, Y and Z are considered to be in            the same output order direction from X when both            DiffPicOrderCnt(X, Y) and DiffPicOrderCnt(X, Z) are positive            or both are negative.

In this manner, source device 102 represents an example of a deviceconfigured to determine a picture order count most significant hit cyclevalue, signal a flag in a parameter set indicating the presence ofsyntax in a slice header indicating a picture order count mostsignificant bit cycle value, and signal values for syntax elements in aslice header indicating a picture order count most significant bit cyclevalue.

Referring again to FIG. 1, interface 108 may include any deviceconfigured to receive data generated by data encapsulator 107 andtransmit and/or store the data to a communications medium. Interface 108may include a network interface card, such as an Ethernet card, and mayinclude an optical transceiver, a radio frequency transceiver, or anyother type of device that can send and/or receive information. Further,interface 108 may include a computer system interface that may enable afile to be stored on a storage device. For example, interface 108 mayinclude a chipset supporting Peripheral Component Interconnect (PCI) andPeripheral Component Interconnect Express (PCIe) bus protocols,proprietary bus protocols, Universal Serial Bus (USB) protocols, I²C, orany other logical and physical structure that may be used tointerconnect peer devices.

Referring again to FIG. 1, destination device 120 includes interface122, data decapsulator 123, video decoder 124, and display 126.Interface 122 may include any device configured to receive data from acommunications medium. Interface 122 may include a network interfacecard, such as an Ethernet card, and may include an optical transceiver,a radio frequency transceiver, or any other type of device that canreceive and/or send information. Further, interface 122 may include acomputer system interface enabling a compliant video bitstream to beretrieved from a storage device. For example, interface 122 may includea chipset supporting PCI and PCIe bus protocols, proprietary busprotocols, USB protocols, PC, or any other logical and physicalstructure that may be used to interconnect peer devices. Datadecapsulator 123 may be configured to receive and parse any of theexample parameter sets described herein.

Video decoder 124 may include any device configured to receive abitstream (e.g., a MCTS sub-bitstream extraction) and/or acceptablevariations thereof and reproduce video data therefrom. Display 126 mayinclude any device configured to display video data. Display 126 maycomprise one of a variety of display devices such as a liquid crystaldisplay (LCD), a plasma display, an organic light emitting diode (OLED)display, or another type of display. Display 126 may include a HighDefinition display or an Ultra High Definition display. It should benoted that although in the example illustrated in FIG. 1, video decoder124 is described as outputting data to display 126, video decoder 124may be configured to output video data to various types of devicesand/or sub-components thereof. For example, video decoder 124 may beconfigured to output video data to any communication medium, asdescribed herein.

FIG. 6 is a block diagram illustrating an example of a video decoderthat may be configured to decode video data according to one or moretechniques of this disclosure. In one example, video decoder 600 may beconfigured to decode transform data and reconstruct residual data fromtransform coefficients based on decoded transform data. Video decoder600 may be configured to perform intra prediction decoding and interprediction decoding and, as such, may be referred to as a hybriddecoder. Video decoder 600 may be configured to parse any combination ofthe syntax elements described above in Tables 1-10. Video decoder 600may perform video decoding based on the values of parsed syntaxelements. For example, different video decoding techniques may beperformed based on whether a picture is of a particular type.

In the example illustrated in FIG. 6, video decoder 600 includes anentropy decoding unit 602, inverse quantization unit and transformcoefficient processing unit 604, intra prediction processing unit 606,inter prediction processing unit 608, summer 610, post filter unit 612,and reference buffer 614. Video decoder 600 may be configured to decodevideo data in a manner consistent with a video coding system. It shouldbe noted that although example video decoder 600 is illustrated ashaving distinct functional blocks, such an illustration is fordescriptive purposes and does not limit video decoder 600 and/orsub-components thereof to a particular hardware or softwarearchitecture. Functions of video decoder 600 may be realized using anycombination of hardware, firmware, and/or software implementations.

As illustrated in FIG. 6, entropy decoding unit 602 receives an entropyencoded bitstream. Entropy decoding unit 602 may be configured to decodesyntax elements and quantized coefficients from the bitstream accordingto a process reciprocal to an entropy encoding process. Entropy decodingunit 602 may be configured to perform entropy decoding according any ofthe entropy coding techniques described above. Entropy decoding unit 602may determine values for syntax elements in an encoded bitstream in amanner consistent with a video coding standard. As illustrated in FIG.6, entropy decoding unit 602 may determine a quantization parameter,quantized coefficient values, transform data, and predication data froma bitstream. In the example, illustrated in FIG. 6, inverse quantizationunit and transform coefficient processing unit 604 receives aquantization parameter, quantized coefficient values, transform data,and predication data from entropy decoding unit 602 and outputsreconstructed residual data.

Referring again to FIG. 6, reconstructed residual data may be providedto summer 610 Summer 610 may add reconstructed residual data to apredictive video block and generate reconstructed video data. Apredictive video block may be determined according to a predictive videotechnique (i.e., intra prediction and inter frame prediction). Intraprediction processing unit 606 may be configured to receive intraprediction syntax elements and retrieve a predictive video block fromreference buffer 614. Reference buffer 614 may include a memory deviceconfigured to store one or more frames of video data. Intra predictionsyntax elements may identify an intra prediction mode, such as the intraprediction modes described above. Inter prediction processing unit 608may receive inter prediction syntax elements and generate motion vectorsto identify a prediction block in one or more reference frames stored inreference buffer 616. Inter prediction processing unit 608 may producemotion compensated blocks, possibly performing interpolation based oninterpolation filters. Identifiers for interpolation filters to be usedfor motion estimation with sub-pixel precision may be included in thesyntax elements. Inter prediction processing unit 608 may useinterpolation filters to calculate interpolated values for sub-integerpixels of a reference block. Post filter unit 614 may be configured toperform filtering on reconstructed video data. For example, post filterunit 614 may be configured to perform deblocking and/or Sample AdaptiveOffset (SAO) filtering, e.g., based on parameters specified in abitstream. Further, it should be noted that in some examples, postfilter unit 614 may be configured to perform proprietary discretionaryfiltering (e.g., visual enhancements, such as, mosquito noisereduction). As illustrated in FIG. 6, a reconstructed video block may beoutput by video decoder 600. In this manner, video decoder 600represents an example of a device configured to parse a flag in aparameter set indicating the presence of syntax in a slice headerindicating a picture order count most significant bit cycle value,conditionally parse values for syntax elements in a slice headerindicating a picture order count most significant bit cycle value basedon the value of the flag in the parameter set and determine a pictureorder count most significant bit cycle value.

In one or more examples, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium and executedby a hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transitory media, but areinstead directed to non-transitory, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor,” as used herein may referto any of the foregoing structure or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated hardware and/or software modules configured for encoding anddecoding, or incorporated in a combined codec. Also, the techniquescould be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Moreover, each functional block or various features of the base stationdevice and the terminal device used in each of the aforementionedembodiments may be implemented or executed by a circuitry, which istypically an integrated circuit or a plurality of integrated circuits.The circuitry designed to execute the functions described in the presentspecification may comprise a general-purpose processor, a digital signalprocessor (DSP), an application specific or general applicationintegrated circuit (ASIC), a field programmable gate array (FPGA), orother programmable logic devices, discrete gates or transistor logic, ora discrete hardware component, or a combination thereof. Thegeneral-purpose processor may be a microprocessor, or alternatively, theprocessor may be a conventional processor, a controller, amicrocontroller or a state machine. The general-purpose processor oreach circuit described above may be configured by a digital circuit ormay be configured by an analogue circuit. Further, when a technology ofmaking into an integrated circuit superseding integrated circuits at thepresent time appears due to advancement of a semiconductor technology,the integrated circuit by this technology is also able to be used.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A method of signaling picture count informationfor decoding video pictures, the method including: sending a pictureorder count (POC) most significant bit (MSB) first flag indicating thata picture order count most significant bit second flag is present;sending the POC MSB second flag to indicate whether a POC MSB cycleelement is present; and when a value of the POC MSB second flag is true,sending the POC MSB cycle element specifying a value of a POC MSB cycle,wherein said flags and cycle element are for use by a decoder to decodethe video picture, wherein the value of the POC MSB cycle is used by thedecoder to compute a POC MSB value that combined with a POC leastsignificant bit (LSB) value produces a POC value used for decoding thefirst video picture, wherein a length of the POC LSB value is based on amaximum POC LSB minus four value.
 2. The method of claim 1, whereinsending the POC MSB first flag comprises sending the POC MSB first flagas a sequence parameter for a sequence of video pictures.
 3. The methodof claim 2, wherein the sequence parameter is included in the sequenceparameter set (SPS) header associated with the sequence of videopictures.
 4. The method of claim 3, wherein the SPS header is specifiedin an SPS Raw Byte Sequence Payload (RBSP) syntax for the sequence ofvideo pictures.
 5. The method of claim 3, wherein the POC MSB secondflag and the POC MSB cycle element are associated with a video picturein the sequence of video pictures.
 6. The method of claim 1, wherein thePOC MSB second flag is a POC MSB present flag.
 7. The method of claim 6,wherein when the value of the POC MSB present flag is false, the POC MSBcycle element specifying a value of the POC MSB cycle is not sent. 8.The method of claim 1, wherein the POC MSB second flag is associatedwith a first video picture.
 9. The method of claim 8 further comprising:sending another POC MSB second flag that is associated with a secondvideo picture and that indicates that a POC MSB cycle element is notpresent; and foregoing sending the POC MSB cycle element for decodingblocks of the second video picture.
 10. The method of claim 1, whereinthe POC MSB cycle element is a variable-length element, wherein a lengthof the POC MSB cycle element is based on a value of at least one otherelement.